Not applicable.
The present invention relates to an apparatus and method for dynamically blending two or more fluids to form a blended gaseous mixture which is delivered via a distribution header to one or more tools for chemical vapor deposition, including epitaxial film growth or similar layer deposition processes. Although the invention may have other applications, it is particularly applicable in semiconductor fabrication.
Semiconductor manufacturers often use a deposition gas mixture of trichlorosilane (SiHCl3) (TCS) and hydrogen (H2) for growth of thin films (e.g., epitaxial silicon) on silicon wafers. Such a mixture is usually obtained by sparging or bubbling H2 gas into TCS liquid held at a specified temperature in a bubbler apparatus. This apparatus delivers a H2 gas carrier stream saturated with TCS into a process tool used in semiconductor fabrication. However, since the stream must be saturated to ensure a consistent composition into the process tool, the bubbler must be located at close proximity to the process tool to avoid condensation in the customer""s supply line (because condensation would affect the stream composition). Consequently, each tool typically has its own bubbler, which significantly increases capital expenditures required to handle TCS and reduces the available floor space in semiconductor fabrication facilities.
It is desired to have a delivery system and method which provide consistent composition of a blended gaseous mixture at a non-saturated condition (i.e., lower TCS dewpoint).
It is further desired to have a distribution header from which the blended gaseous mixture could be delivered to multiple tools, which would reduce floor space requirements and save capital.
It is still further desired to have the ability to provide a blended gaseous mixture to a variable number of process tools while maintaining consistent stream composition.
It is still further desired to have the ability to quickly manipulate the stream composition when end user requirements fluctuate.
The present invention is a dynamic blending gas delivery system and method. The present invention also includes a blended gaseous mixture produced in accordance with the dynamic blending method. The blended gaseous mixture is used in chemical vapor deposition tools or other similar process tools, such as tools used in epitaxial film growth.
A first embodiment of the invention is a method for processing a plurality of fluids to form a blended gaseous mixture and supplying the blended gaseous mixture to a distribution header from which the blended gaseous mixture is delivered to at least one chemical vapor deposition tool or similar process tool. The method comprises seven steps. The first step is to supply a first fluid. The second step is to heat the first fluid to a temperature where at least some portion of the first fluid is a vapor. The third step is to superheat the vapor portion of the first fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool. The fourth step is to supply a second fluid. The fifth step is to heat the second fluid to a temperature sufficient to avoid condensation of the superheated vapor portion of the first fluid when the superheated vapor portion comes in contact with the second fluid. The sixth step is to combine the heated second fluid and the superheated vapor portion of the first fluid to form a blended gaseous mixture having desired physical and chemical properties for chemical vapor deposition, epitaxial film growth, or a similar process. The final step is to deliver the blended gaseous mixture to the distribution header from which the blended gaseous mixture is delivered to the at least one chemical vapor deposition tool or similar process tool.
In the described apparatus and process, the first fluid is trichlorosilane (SiHCl3) (TCS) and the second fluid is hydrogen (H2). However, the invention may be used to dynamically blend and deliver other vapor deposition fluids. For example, it may be used with other first fluids, including but limited to, silicon tetrachloride (SiCl4), dichlorosilane (SiH2Cl2), tetraethylorthosilicate (TEOS), phosphorus oxychloride (POCl3), trimethylsilane (SiH(CH3)3), boron trichloride (BCl3), and tungsten hexafluoride (WF6). Other possible second fluids include, but are not limited to, helium, nitrogen, argon, and oxygen.
A second embodiment of the invention is a method which includes the additional step of automatically maintaining a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture. In one variation of this embodiment, the step of automatically maintaining a desired flow ratio between the first and second fluids comprises the following sub-steps: (a) measuring a flow rate of the first fluid; (b) measuring a flow rate of the second fluid; (c) measuring a change in pressure inside the distribution header; and (d) adjusting the flow rates of the first and second fluids at the desired flow ratio proportionally in an inverse relation to a measured change in pressure inside the distribution header.
A third embodiment includes three steps in addition to the steps in the first embodiment discussed above. The first additional step is to supply a third fluid which does not react with the first or second fluids or with the blended gaseous mixture. The next additional step is to heat the third fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool. The final additional step is to combine an amount of the heated third fluid in the gaseous phase with the blended gaseous mixture whereby a desired molar ratio of the first and second fluids is maintained so as to maintain the desired physical and chemical properties of the blended gaseous mixture and whereby condensation of the blended gaseous mixture is avoided in the distribution header. In one variation of this embodiment, the third fluid is an inert gas.
A fourth embodiment has one step in addition to the steps in the third embodiment. The additional step is to automatically maintain a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture.
A fifth embodiment has two steps in addition to the steps in the first embodiment. The first additional step is to provide a storage buffer upstream of the distribution header. The second additional step is to deliver the blended gaseous mixture to the storage buffer prior to delivering the blended gaseous mixture to the distribution header.
A sixth embodiment is a dynamic blending gas delivery system for supplying a blended gaseous mixture to a distribution header from which the blended gaseous mixture is delivered to at least one chemical vapor deposition tool or similar process tool. The system includes: (1) means for supplying a first fluid; (2) means for heating the first fluid to a temperature where at least some portion of the first fluid is a vapor; (3) means for superheating the vapor portion of the first fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool; (4) means for supplying a second fluid; (5) means for heating the second fluid to a temperature sufficient to avoid condensation of the superheated vapor portion of the first fluid when the superheated vapor portion comes in contact with the second fluid; (6) means for combining the heated second fluid and the superheated vapor portion of the first fluid to form a blended gaseous mixture having desired physical and chemical properties for chemical vapor deposition, epitaxial film growth, or a similar process; and (7) means for delivering the blended gaseous mixture to the distribution header from which the blended gaseous mixture is delivered to the at least one chemical vapor deposition tool or similar process tool.
In the preferred embodiment, the first fluid is trichlorosilane (TCS) and the second fluid is hydrogen (H2). However, fluids other than TCS may be used as the first fluid, including but not limited to silicon tetrachloride (SiCl4), dichlorosilane (SiH2Cl2), tetraethylorthosilicate (TEOS), phosphorus oxychloride (POCl3), trimethylsilane (SiH(CH3)3), boron trichloride (BCl3), and tungsten hexafluoride (WF6). Other possible second fluids include, but are not limited to, helium, nitrogen, argon and oxygen.
A seventh embodiment is a dynamic blending gas delivery system which is like the sixth embodiment but includes means for automatically maintaining a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture. In the preferred embodiment, the means for automatically maintaining a desired flow ratio between the first and second fluids is a flow ratio controller.
In another variation of the seventh embodiment, the means for automatically maintaining a desired flow ratio between the first and second fluids includes: (1) means for measuring a flow rate of the first fluid; (2) means for measuring a flow rate of the second fluid; (3) means for measuring a change in pressure inside the distribution header; and (4) means for adjusting the flow rates of the first and second fluids at the desired flow ratio proportionally in an inverse relation to the measured change in pressure inside the distribution header.
A variation of this embodiment is an eighth embodiment, which includes the following additional elements: (1) a first sensor for sensing the flow rate of the first fluid and for providing a signal indicative thereof; (2) a second sensor for sensing the flow rate of the second fluid and for providing a signal indicative thereof; (3) a third sensor for sensing the change in pressure inside the distribution header and for providing a signal indicative thereof; and (4) a computer for receiving signals from the first, second, and third sensors, determining the flow rates of the first and second fluids, determining the change in pressure inside the distribution header, determining any adjustments required in the flow rates of the first and second fluids in order to maintain the desired flow ratio, and sending at least one signal indicative of the required adjustments in the flow rates to a flow ratio controller. In the preferred embodiment, the computer is a programmed logic controller.
A ninth embodiment includes three elements in addition to those in the sixth embodiment discussed above. The three additional elements are: (1) means for supplying a third fluid which does not react with the first or second fluids or with the blended gaseous mixture; (2) means for heating the third fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool; and (3) means for combining an amount of the heated third fluid in a gaseous phase with the blended gaseous mixture whereby a desired molar ratio of the first and second fluids is maintained and whereby condensation of the blended gaseous mixture is avoided in the distribution header. In a preferred embodiment, the third fluid is an inert gas, such as argon or helium.
A tenth embodiment has one step in addition to the steps in the ninth embodiment. The additional step is to automatically maintain a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture.
An eleventh embodiment of the invention includes two elements in addition to those in the sixth embodiment discussed above. The two additional elements are: (1) a storage buffer upstream of the distribution header; and (2) means for delivering the blended gaseous mixture to the storage buffer prior to delivering the blended gaseous mixture to the distribution header.
In a twelfth embodiment, the dynamic blending gas delivery system includes means for purging the system.
A thirteenth embodiment is a system for blending and delivering a deposition process gas to at least one chemical vapor deposition tool or similar process tool. The system includes the following: (1) a distribution header for accumulating a deposition process gas and for distributing the deposition process gas to each tool in response to a demand from the tool; (2) a sensor in communication with the distribution header for determining a pressure drop in the distribution header caused by a change in flow of deposition process gas from the distribution header; (3) a supply of liquid deposition material; (4) a heater for vaporizing the liquid deposition mate rial and superheating the resulting vapor; (5) a first flow controller for controlling a rate of flow of the superheated vapor from the heater to the distribution header; and (6) means for regulating the first flow controller to allow a flow of the superheated vapor proportional in an inverse relation to a change in pressure inside the distribution header.
A fourteenth embodiment includes the following elements in addition to those in the thirteenth embodiment: (1) at least one supply of at least one carrier gas; (2) an additional flow controller in communication with each supply of carrier gas for controlling a rate of flow of each carrier gas; (3) means for regulating the additional flow controller to allow a flow rate in a pre-selected ratio to the mass flow rate of the superheated vapor through the first flow controller; (4) dynamic blending means for blending each flow-controlled carrier gas with the flow-controlled superheated vapor; and (5) means for delivering the resulting blended gaseous mixture to the distribution header. In one variation of this embodiment, there are at least two carrier gases at least one carrier gas being a reactive material and at least one carrier gas being an inert material.
A fifteenth embodiment is similar to the fourteenth embodiment but includes the additional element of heating means for raising the temperature of each carrier gas above the dewpoint of the superheated vapor prior to blending.
Another aspect of the invention is the blended gaseous mixture produced in accordance with the methods discussed above, including but not limited to the methods in the first and third embodiments.